Layered double hydroxides for the development of 3D scaffolds in skin tissue engineering

Póster presentado en EUROCLAY 2023: International Conference of European Clay Groups Association. Bari (Italy), 24-27 July 2023Skin wound healing is a multiphase process that involves a series of biological responses following an injury. However, if its progression is altered or if an underlying disease (e.g. metabolic disorders, infections) is present, the wound could become chronic, posing significant health problems [1]. Three-dimensional structures, such as microfibers and microparticles, could act as scaffold which stimulate skin reparation [2]. Clay minerals are well known additives in the development of such scaffolds [3]. Among these, anionic clays like layered double hydroxides (LDH) have already been reported as drug delivery systems or as polymer additives in materials science for biomedical purposes. The combination of their peculiar structure and chemical composition should contribute to support cellular processes [4]. Therefore, the aim of this work was the development of spray-dried microparticles based on ZnAl LDH doped sodium alginate, to enhance the skin tissue regeneration. LDH based on Zn2+ were selected since Zn2+ proved to enhance wound healing and to be effective as antimicrobial. LDH containing Zn and Al were synthesized via co-precipitation using ammonia as an alkaline agent. The LDH were then isolated upon centrifugation and dispersed, without further washing, in water under stirring. Sodium alginate was added to the dispersion, which was then spray dried. The microparticles were then crosslinked with CaCl2 [5]. The spray drying process leads to the formation of smooth microparticles with a spheroidal shape. The presence of LDH slightly alters their morphology, which is evident by the hexagonal lamellar platelets visible on their surface. The crosslinking step with CaCl2 allows to obtain water insoluble microparticles without changes in morphology, dimensions as well as LDH loading. In all cases, the mean diameters of the microparticles range from 6 to 8 ¿m and the LDH doping slightly increases the diameters. To conclude, it was possible to manufacture sodium alginate microparticles doped with synthetic LDH, based on Zn and Al, and to obtain water insoluble matrixes using crosslinking with CaCl2. These were intended for skin tissue engineering. Mechanical properties, ions release, and preclinical characterizations will be performed to investigate the systems safety and efficacy. Further characterizations will be performed to clarify the LDH role in polymeric matrix performance and tissue regeneration

Green approaches for the synthesis of layered double hydroxides and evaluation of their biological properties

Comunicación oral presentada en International Conference of European Clay Groups Association - EUROCLAY 2023, Bari (Italy.), 24-27 july 2023Layered double hydroxides (LDH) consist of brucite-like layers containing di- and trivalent metal ions with interchangeable counter anions and solvation molecules that are present between the layers [1]. LDH find several applications in the pharmaceutical field due to their chemical stability, biocompatibility and high mechanical strength, and they are well known to support cellular processes, such as cell differentiation and viability [2]. LDH have very high potentialities for industrial applications, but their synthesis often requires a high number of steps, which could also lead to the production of great amounts of waste [3]. Given these premises, the goal of the work is the design of sustainable strategies for the synthesis of LDH in view of a continuous manufacturing process. LDH were produced through two well-known methods using new green synthesis conditions and their properties were compared to investigate the differences given by the LDH compositions. In particular, their biological properties were considered for a future application in the biomedical field, especially in tissue engineering. Nitrate salts of Mg2+, Zn2+, Cu2+, Al3+, and Fe3+, chosen as bio-enabling cations, were used. First, a co-precipitation method through a fast addition of salts and reduced aging time was developed, using ammonia as an alkaline agent. Few studies are reported using this chemical for the synthesis of LDH. Being a volatile molecule, the excess of ammonia could be easily removed and trapped, together with some of the byproducts that might be formed during the process. Second, the urea hydrolysis through microwave and hydrothermal treatment was considered. The synthesis parameters were adjusted to minimize the waste production. In all cases, the LDH were characterized both as prepared and upon centrifugation/washing, in view of a single step synthesis without water and components waste. The XRD patterns showed that LDH phases represent the major part in the unwashed samples. Both the presence of ammonia and the washing step could affect the interlayer anions (NO3 ¿, CO3 2-, [NH4(NH3)n]+) in the structure. Several techniques (TEM, DLS, BET, TGA, ICP/CHN) were used to screen the different LDH and to get a correlation between their composition and their physico-chemical and biological properties. Considering a future application in the biomedical fields, the antioxidant properties alongside cell viability on different cell lines (fibroblasts, Caco-2 and tenocytes) were investigated. In conclusion, sustainable green approaches were used to produce promising LDH for the development of composite materials to be used in biomedical field through continuous manufacturing processes.

Design and development of polydioxanone scaffolds for skin tissue engineering manufactured via green process

Fiber spinning technologies attracted a great interest since the beginning of the last century. Among these, electrospinning is a widely diffuse technique; however, it presents some drawbacks such as low fiber yield, high energy demand and the use of organic solvents. On the contrary, centrifugal spinning is a more sustainable method and allows to obtain fiber using centrifugal force and melted materials. The aim of the present work was the design and the development of polydioxanone (PDO) microfibers intended for tissue engineering, using centrifugal spinning. PDO, a bioresorbable polymer currently used for sutures, was selected as low melting polyester and DES (deep eutectic solvents), either choline chloride/citric acid (ChCl/CA) or betaine/citric acid (Bet/CA) 1:1 M ratio, were used to improve PDO spinnability. Physical mixtures of DES and PDO were prepared using different weight ratios. These were then poured into the spinneret and melted at 140 degrees C for 5 min. After the complete melting, the blends were spun for 1 min at 700 rpm. The fibers were characterized for physico chemical properties (morphology; dimensions; chemical structure; thermal behavior; mechanical properties). Moreover, the preclinical investigation was performed in vitro (biocompatibility, adhesion and proliferation of fibroblasts) and in vivo (murine burn/excisional model to assess safety and efficacy). The multidisciplinary approach allowed to obtain an extensive characterization to develop PDO based microfibers as medical device for implant to treat full thickness skin wounds